What is High Strength Concrete (HSC)

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• What is High Strength Concrete (HSC)
• Technology of HSC
• Availability of HSC
• Specification and Approval of HSC

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What is High Strength Concrete?

• Definitions
• BS EN 206-1 gt C60 _at_ 28 days
• ACI gt C41 _at_ 56 or 90days
• HSC High Performance Concrete (HPC)
• HPC is not always HSC
• Is C60 _at_ 28 days HSC?
• Is C30 _at_ 2 days HSC?

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• HESC HSC

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HSC Technology

• The methods and technology for designing HSC are
  not substantially different from those required
  for normal strength concrete.
• However, different considerations have to be
  taken into account as the strength requirement
  increases
• Aggregate type
• Aggregate size
• Chemical admixtures
• Cement types
• Additions

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HSC Technology

• Coarse Aggregate type
• A wide range of aggregates can be used
• Not all aggregate types are suitable
• Ceiling Strength
• Crushed rock
• Angular
• Strong
• Clean
• Durable

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HSC Technology

• Recycled Aggregate
• Reduces strength
• Increase cement content
• BS8500-2 limits the use of Recycled Aggregates to
  classes up to C40/50.

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HSC Technology

• Coarse Aggregate size
• At higher strengths smaller aggregate size is
  beneficial.
• reduced micro cracks
• larger surface area and greater distribution of
  bond stress

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HSC Technology
Chemical Admixtures

• HSC
• High range water reducers
• WC ratio 0.45 lt C60
• WC ratio 0.3 0.35 gtC60

• HESC
• Accelerators
• Set lt 8hrs (affect workability)
• Hardening 8 - 48hrs

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HSC Technology

• Cement Types
• HSC can be produced with all cement types
  available in the UK
• CEMII CEMIII cements give additional benefits
• reduced heat of hydration
• Reduced risk of early age thermal cracking
• increased ultimate strength
• reduced permeability
• Improved resistance to physical and chemical
  attack
• energy-saving and sustainable

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HSC Technology

• Additions
• Silica fume
• mineral admixture - composed of submicron
  particles of silicon dioxide, manufactured as a
  co-product from the production of silicon and
  ferrosilicon metal.
• Metakaolin
• formed when china clay, the mineral kaolin, is
  heated to a temperature between 600 and 800ºC

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HSC Technology

• Production
• There are no specific requirements for mixing of
  HSC, although a forced-action mixer is preferred.
• Factors which have only a second order effect at
  lower strength levels may become of major
  importance at higher levels

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HSC Technology

• Quality Control
• EN206-1 Annex H gives additional provisions for
  production of HSC
• Control of
• constituent materials
• equipment
• production procedures
• concrete properties

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Availability of HSC

• In general terms, all BRMCA Member companies can
  produce and supply HSC from any Ready Mixed
  Concrete Plant, given sufficient notice and
  preparation time.
• However, there are a number of issues that need
  to be considered.

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HSC Availability at Ready Mixed Concrete Plants
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Availability of HSC

• Are appropriate aggregates stocked?
• Can appropriate aggregates be imported?
• Are sufficient aggregate storage bins available?
• Is the use of additional aggregate sources
  compatible with plant capacity and existing
  supply requirements?
• Generally none of these factors are issues of
  great concern in major UK cities

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Availability of HSC

• HSC is not currently widely specified in terms of
  overall concrete volume.
• Planning is the key, with as much information
  supplied as early as possible at the
  enquiry/order stage.

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Specification Approval of HSC

• Concrete specifications should be in accordance
  with BS 8500 -1 specifically Clauses 4.3 and 5.0
  (Designed Concrete Exchange of Information)
• The specification documents should be concise and
  complete enabling the supplier to immediately
  consider the specification data without having to
  first interpret a new format.

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Specification Approval of HSC

• Specifications should be performance based.
• They should state the required properties of the
  hardened and fresh concrete, but should otherwise
  be free of unnecessary restrictions e.g. maximum
  cement content permissible cement types
• This means that much of the responsibility for
  ensuring that these qualities are achieved lies
  with the supplier.
• This is appropriate, since the concrete supplier
  is producing concrete on a daily basis and
  therefore is likely to have much greater
  expertise relating to concrete production than
  any other party in the construction process.

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Specification Approval of HSC

• The concrete supplier can then provide
• Mix Design Certificates (giving guidance on
  constituent quantities although these can vary)
• Supply History in terms of Previous data or long
  term experience (EN 206-1 Annex A)
• Plant Specific Information (Supplying Plant or
  Plants)
• Details of Backup Facilities/Plants
• The Ready Mixed Concrete companies are more
  than happy to attend design meetings and discuss
  the specifics of construction and pour
  requirements.

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Specification Approval of HSC

• Trial Mixes
• EN206-1 Annex A Initial tests states that
  Trials may not be necessary if sufficient
  evidence re Previous Data or Long Term
  Experience is available
• Laboratory or Site Trials may be undertaken if
  required with a detailed report produced
  indicating performance criteria in terms of the
  required performance characteristics

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What is HSC?

• HSC gt 60 N/mm2
• Straightforward, in accordance with
• BS EN 12350 1 (sampling)
• BS EN 12390 1 (moulds)
• BS EN 12390 2 (making curing)
• BS EN 12390 3 (testing)
• BS EN 12390 4 (test machine)

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What is HESC

• Not straightforward
• 5 N/mm2 at 12 hours
• 15 N/mm2 at 15 18 hours
• 22-25 N/mm2 at 60 hours
• Temperature?

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What next?

• There is a clear requirement for HESC?
• BRMCA CONSTRUCT must work together.
• Develop a standard specification for HESC
• Conformity rules

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Selection of Recent Projects Across the UK

• Snow Hill Residential Tower, Birmingham, C60
  C75 Supplied
• Kincardine Bridge, Fife, C80 C100 Supplied
• New Street Square, London C60 C80 Supplied
• Pioneer point, Ilford, C85 Supplied
• St. James Road, Croydon, C90 Supplied
• Bridgewater Place, Leeds, C60 Supplied
• Green Quarter, Manchester, C60 Supplied
• Note Compressive Cube Strength Shown.

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• New Street Square
• London
• C80

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• Green Quarter
• Manchester
• C60

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• Bridgewater Place
• Leeds
• C60

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• Civil Courts
• Manchester
• C60

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Kincardine Bridge Scotland C100
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HSC compressive strength